The cooperative of Arcachon boatmen, and the default way to get out onto the bay without hiring anyone privately. The standard run is the Île aux Oiseaux — an hour and a quarter through the oyster beds to look at the cabanes tchanquées, the two stilt huts that have become the emblem of the whole basin — with a longer two-hour circuit that goes right around the island.
Other departures head the other way, out towards the mouth of the bay, the Banc d'Arguin sandbank and the Dune du Pilat seen from the water, which is the angle that makes sense of how big it is. There are also lunch and dinner cruises.
Book at least 24 hours ahead; the boarding point is confirmed by email, because it changes with the tide and the season.